Depending on what fill station you have for your air rifle you may be able to just buy the female connecter that screws in where you usually put you air rifle bottle. Just a case of unscrewing/screwing in the female adapter in between filling marker/air rifle.
This is what i did, with mine. My fill rig has the thread that takes the logun sweet 16 air rifle bottle, Just find a company that supplies high pressure air fittings and explain what you want.
Just make sure your filling adapter will handle the pressure required for filling your marker as well, just to be safe.